The present invention relates to apparatus for cutting stacks of paper sheets or the like, and more particularly to improvements in apparatus for trimming the head, foot and front ends of brochures, pamphlets, books or like accumulations of overlapping sheets. Still more particularly, the invention relates to improvements in apparatus for trimming three different sides of each of a series of successive stacks of sheets by three discrete cutting implements.
An apparatus with three discrete knives for the trimming of head, foot and front ends of brochures or the like is disclosed in Swiss Pat. No. 340,479. The patented apparatus comprises a first severing station where two discrete knives trim the head and foot ends of brochures, and a second severing station at which a third knife trims the front ends of the brochures. An initial cycle of operation involves the trimming of a brochure at the first station and transport of the thus treated brochure to the second station. During the next cycle, the brochure is trimmed by the knife at the second station and is removed from the apparatus. The patented apparatus exhibits the advantage that a substantial part of each cycle is available for transport of brochures so that the apparatus can treat a large number of brochures per unit of time. However, the patented apparatus also exhibits a serious drawback, namely, that each brochure must be properly centered at two different stations, i.e., at the first station preparatory to trimming by the knives which remove material at the head and foot ends, and thereupon at the second station preparatory to removal of material from the front end. Accurate centering presents serious problems, especially when the brochures to be trimmed are transported at a high speed. Therefore, the quality of treatment in the patented apparatus is not entirely satisfactory, especially if the brochures are transported at an elevated speed.